When metal surfaces are treated with aqueous solutions or are rinsed with water, troublesome residues of liquid adhere to them. Liquid residues of this type cause problems in certain processing operations, for example, during the heating of cans or tins for preserved foods, insofar as they either dry out, forming unseemly stains, or leave behind a grey water haze. Also, in the event of subsequent contact with foods, it is not always possible to prevent undesirable changes, for example, in taste, from occurring. In instances such as these, therefore, it is advantageous if the residues are as small as possible and can be largely removed, for example, by treatment with hot air. However, treatment with hot air alone is unsatisfactory in view of the energy considerations.
For this reason, attempts have already been made to reduce residues of liquid adhering to metal surfaces by use of special additives. It is known that quaternary ammonium compounds may be used for this purpose. They are added either to the rinsing baths or to the actual treatment solutions for metal surfaces, which may contain, in addition to inorganic and/or organic acids, sodium hydroxide, potassium hydroxide, soda, surfactants, complexing agents, and inhibitors as well as solution promoters. With solutions such as these used in a concentration of 1% by weight, a residual water content of about 10 g/m.sup.2 is obtained for a quaternary ammonium compound content of from about 0.05 to 1 gm/liter. With the same solutions used in the same concentration, but without any quaternary ammonium compounds added, the residual water content amounts to from about 20 to 40 gm/m.sup.2, dependent upon the drainage time.
However, the use of quaternary ammonium compounds is unsatisfactory in many respects. Quaternary ammonium compounds foam too vigorously and, because of this, cannot be applied by spraying. In addition, even the smallest traces cause further processing problems with certain foods because there is the danger of migration from the interface into the food. Finally, quaternary ammonium compounds cannot be used with solutions containing surface-active anionic substances.